2002 GTX 1503 4-Tec compression issue.

[Juju481]

Hey everyone,


Looking for some insight or shared experiences from anyone who's dealt with something similar.


I’ve got a Sea-Doo with the 1503 4-TEC engine. my 2002 GTX died on me while cruising a few weekends ago. I recently ran a compression test and found that two adjacent cylinders are about at about 40 PSI, the third is fine. The readings were consistent across multiple tests with a good tester and warm engine.


A bit of context:

• The engine still cranks and runs, but you can tell something’s off.
• No major signs of oil contamination or external damage.
• It hasn’t been sunk or overheated (as far as I know), and maintenance has been decent.
• It's a 4-stroke, N/A 1503 (not SCIC).

Before I start tearing into it, I’d appreciate any ideas or suggestions:

• Could this point to a blown head gasket between cylinders?
• Burnt valves or valve seat issues? (but doesn't make sense to me to be two cylinders)
• Possible piston ring damage or cylinder scoring? (you'd think it would be only in one cylinder)
• Is this something common in these engines at higher hours?

Any specific tests, visual inspections, or next steps you'd recommend before pulling the head? Also, if anyone has seen this exact issue on a 1503, I’d love to hear how it turned out.


Thanks in advance — all input is appreciated!

 

[tobytd]

My GUESS head gasket

 

[dcm0123]

Or valves- take head off and turn so combustion chamber is facing up. Pour into combustion area either gas or mineral spirits and see if it flows past the valves.

 

[Juju481]

Turns out I have a snapped timing chain, and two of the rocker assemblies are snapped in half. Considering pulling the head and checking lower end for damage. Guy on marketplace is selling a complete head for $500. Might try and fix. Thoughts??

 

[dcm0123]

Take it apart first. Rockers may have snapped because valves hit pistons when chain broke.
If there are signs of corrosion on head gasket surface of new head or is older that 2007, I would pass on it.
Pre 2007 heads have weak hollow valve stems with heads which pop off and ruin engines.

You are probably looking at least $1500 in misc parts to put this back together and 60-80 hours to disassemble and reassemble,. Most internal engine bolts are one time use. Engine will have to come out and requires major disassembly to replace the chain.

 

[Juju481]

Wondering if it’s worth it. The head is off a 2005, but there’s not alot of complete heads on the market out there…. I was hoping to leave the ending in and take the timing cover off and hopefully be able to slip the timing chain around the crank. From the sounds of your last message that isn’t possible?

 

[dcm0123]

I bought my head from a reputable seller on Ebay who sells Seadoo Parts. $450 for a very clean 2012 year.
I also bought other parts such as drive shaft and piston from folks on Ebay which I returned because people did not know what they are selling. Make sure anything you buy can be returned.

There are a lot of small parts such as thrust washers on the starter gear shaft etc which you need to be careful installing. You are better off pulling the engine to have better access..
If this was a salt water machine you may have problems with the driveshaft which may need to be replaced due to excessive corrosion in the o-ring seal area.
It will likely cost a lot more than you expect.